Suppression of IL-8 production from airway cells by tiotropium bromide in vitro

BACKGROUND: COPD is characterized by persistent and progressive airway inflammation. Although neutrophilic airway inflammation is generally accepted to be a major factor in the pathogenesis of COPD, the influence of the agents used for the treatment of COPD on neutrophil functions such as chemotaxis is not fully understood. PURPOSE: The present study aimed to examine the influence of tiotropium bromide on the production of interleukin (IL)-8 from human airway epithelial cells and lung fibroblasts (LFs) after lipopolysaccharide (LPS) stimulation in vitro. METHODS: BEAS-2B cells, human bronchial epithelial cell line, and LFs, at a concentration of 5 × 10(5) cells/mL, were stimulated with LPS in the presence of various concentrations of tiotropium bromide. IL-8 in culture supernatants was examined by enzyme-linked immunosorbent assay (ELISA). IL-8 messenger ribonucleic acid (mRNA) expression was examined by real-time polymerase chain reaction. The influence of tiotropium bromide on LPS-induced signaling pathways was also analyzed by examining nuclear factor-kappa (NF-κ)B activation and signaling protein phosphorylation by ELISA. RESULTS: Tiotropium bromide at >15 pg/mL inhibited IL-8 production from both BEAS-2B cells and LFs after LPS stimulation. Tiotropium bromide also suppressed IL-8 mRNA expression through the inhibition of NF-κB activation and signaling protein, extracellular-signal-regulated kinase 1/2, and c-Jun N-terminal kinase, phosphorylation. CONCLUSION: The present results strongly suggest that tiotropium bromide exerts the inhibitory effect on neutrophilic inflammation through the suppression of IL-8 production from epithelial cells and LFs by interfering with LPS-mediated signaling pathways and thus may contribute to lower cellular inflammation in COPD, which is responsible for favorable modification of the disease.